521 datasheet(34/96 Pages) INTEL

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Datasheet

Electrical Specifications

2.13

GTL+ FSB Specifications

Termination resistors are not required for most GTL+ signals, as these are integrated into the

processor silicon.Valid high and low levels are determined by the input buffers which compare a

signal’s voltage with a reference voltage called GTLREF. Table 2-18 lists the GTLREF

specifications. The GTL+ reference voltage (GTLREF) should be generated on the system board

using high precision voltage divider circuits.

Table 2-18. GTL+ Bus Voltage Definitions

Symbol

Parameter

Min

Typ

Max

Units

Notes1

NOTES:

Unless otherwise noted, all specifications in this table apply to all processor frequencies.

GTLREF

Bus Reference

Voltage

(0.98 * 0.67) * VTT 0.67 * VTT (1.02 * 0.67) * VTT

2, 3, 4, 5

The tolerances for this specification have been stated generically to enable the system designer to calculate the minimum

and maximum values across the range of VTT.

GTLREF should be generated from VTT by a voltage divider of 1% resistors or 1% matched resistors.

The VTT referred to in these specifications is the instantaneous VTT.

The Intel® 915G/915GV/915P and 910GL Express chipset platforms use a pull-up resistor of 100

Ω and a pull-down resistor

of 210

Ω. Contact your Intel representative for further details and documentation.

PULLUP

On die pullup for

BOOTSELECT

signal

500

—

5000

Ω

These pull-ups are to VTT.

Termination

Resistance

Ω

TT is the on-die termination resistance measured at V

TT/2 of the GTL+ output driver.

COMP[1:0]

COMP Resistance

59.8

60.4

Ω

COMP resistance must be provided on the system board with 1% resistors. COMP[1:0] resistors are to VSS.

521 Datasheet(PDF) 34 Page - Intel Corporation

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